Radio frequency transformer



March 10, 1931.

M. c. BATSEL RADIO FREQUENCY TRANSFORMER Filed April 26, 1923 INVENTOR Max QBafs e/ WITNESSES:

ATTORN EY Patented Mar. 10, 1931 UNITED STATES PATENT OFFICE MAX 0. BATSEL, OF WILKINSBURG, PENNSYLVANIA, ASSIGNOR "10 WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA RADIO FREQUENCY TRANSFORMER Application filed April 26,

My invention relates to wireless receiving systems having particular relation to regenerative radio-frequency amplifying systems.

In its broadest aspect, one object of my invention is to provide a means for regulating the losses in the output circuit of a vacuum-tube device and thereby controlling the proportion of the energy in the output circuit that is delivered to the input circuit.

More specifically stated, it is an object of this invention to control the extent to which energy is fed back into a vacuum-tube device by controlling the losses in a transformer connecting the output circuit thereof to the I input circuit of the next vacuum-tube device in a multi-stage amplifying system.

A further objectof my invention is to provide a transformer which is particularly applicable to coupling the successive stages of a radio-frequency amplification system.

It is a further object of this invention to provide for controlling the losses in a transformer used at radio frequency by adjusting the air gap of such transformer.

The permeability of a transformer core at radiofrequency is very low even when the core is made of thin laminations of material which at lower frequencies is highly permeable. The magnetic leakage in a transformer at such frequencies is consequently large, so that adjusting the air gap will alter the reactance of the windings of such a transformer but slightly, and yet will have a large effect upon the losses occurring in the core. It is an object of this invention to utilize this principle for controlling the losses without substantially altering the reactance in the output circuit of a vacuum-tube device.

Other objects and applications of my invention, as well as details of construction and operation and circuit arrangement, will be apparent more fully hereinafter when taken in connection with the accompanying description, claims and drawing, wherein:

Figure 1 is a diagrammatic view of a cascade-connected, radio-frequency receiving system wherein my invention is employed,

Fig. 2 is a front elevational view of a coupling transformer embodying my invention, and

1923. Serial No. 634,761.

Fig. 3 is a section on the line IIIIII of F i Tnithe illustrative form of embodiment of my invention shown in the drawing, an antenna 1 is connected to a ground 2 through the primary winding 15 of a radio-frequency v transformer 16 and a source 17 of direct-current energy. The secondary winding 18 of the radio-frequency coupling transformer 16 serves to connect the first stage of radio-freto a succeeding stage of radio-frequency amplification effected by a. second radio-frequency amplifying tube 19, the input terminals 21 and 22 of which are connected to the terminals of said secondary winding 18. The radio-frequency transformer 16, which serves to connect the tubes 12 and 19, comprises a finely laminated core preferably of high grade iron or silicon steel having an adjustable air gap. Any convenient means for adjusting the air gap may be employed. In the form chosen for illustration, the transformer core is made in two halves 38 and 39 which come into close proximity within the sleeve 42 upon which the coils 15 and 18 are wound. These two halves are biased toward one another by any convenient means. For example, springs (not shown) may be employed to press against the two halves of the transformer and the housing within which it is contained. The ends 41 outside the sleeve, where the two transformer core halves again approach each other, are separated by a wedge 23 of insulating material Whose position may be adjusted to vary the air gap between said ends 41. r

, quency' amplification efiected by the tube 12 I At radio-frequency below 1000 meters, that is at frequency above 300,000 cycles the permeability of the laminations constituting the core is so small, being ordinarily no more than 2 or 3, that a large proportion of the flux passes through the air. For this reason an increase in the air gap makes but little change in the total flux through the coils 15 and 18 but makes considerable change in the flux passing through the laminations. The losses occurring in the laminations are therefore reduced by Widening the air gap, but

little change in the react-an'ce of the coils 15 and 17 accompanies this change in the losses.

WVhen the air gap is opened to the maximum extent the smallest proportion of the energy in the output circuit, including coil 15, is used to supply these losses and therefore a larger proportion is available for feeding back into the input circuit. On the other hand, when the air gap is nearly closed, a greater proportion of the-energy supplied to the coil 15 must go to care for the core losses and so a smaller proportion is available for delivery to the input circuit.

An outgoing circuit from the radio-frequency amplifying tube 19 extends from the anode 24 thereof through the primary win ding 25 of a coupling transformer 26 and the energy source 17 to the hot cathode or input electrode 22 thereof. The radio-frequency coupling transformer 26, the tube 19 and the input and the output circuits associated therewith, all of which constitute the second stage radio-frequency amplification, are designed to operate in a manner similar to that just described for the first stage of radioffrequency amplification.

The amplified radio-frequency currents in the second stage may be detected by impressing the same upon the input electrodes 27 and 28 of a-detector tube 29, the same being connected to the secondary winding 31 of said coupling transformer 26 through conductors 32 and 33, respectively. A grid-biasing condenser 34', which is shunted by a grid leak 35, .may be included in the grid conductor 32 for reasons known to those skilled in the art. An outgoing circuit forthe detector tube 29 extends from the anode 36 thereof through a telephone or other indicating device 37 and the energy source 17 to the hot cathode 28 thereof.

The transformer 26 has its losses regulated by means of the wedge 23. in a way closely analogous to that already described for the transformer 16.

In the operation of my invention, the Wedges 23- and 23 may be adjusted until the tubes 12 and 19 are just on the point of 0scillating. This givesthe maximum regeneration desired in the amplifying steps.v If less regeneration is desired, the wedges are moved tofshorten the air gaps. These changes produce but little variation in the 'reactance of the windings 15 and 25 so that no troublesome changes in the phase of the feedback current occur. When signal impulses are received in the antenna circuit, the resulting radio-frequency currents are successively regeneratively amplified by the tubes 12 and 19 and then detected by the detector tube 29. The radio-frequency current traversing the plate-filament circuit of the detector tube 29 may be detected by the telephone receivers 37.

While I have described certain features of my invention in detail, and while I have pointed out certain of the most obvious principles and purposes thereof, I do not intend that the language employed in the following claims shall be limited to the precise details described, but I intend that the claims shall be construed to cover all combinations which are fairly included in the language thereof, when readin connection with the prior art, regardless of the details and functions mentioned in thedescription or illustratedin the drawing. 1

I claim as my invention:

1. In combination, an oscillator tube having input and output circuits, said tube and circuits being so designed as to have a high negative damping eifect tending to cause the generation of oscillations, a second tube having an input circuit, anda transformer for coupling said output circuit and said second tube input circuit, said transformer having a variable air gap, whereby the effective resistance introduced into said output circuit by said transformer may be varied, the magnitude of said negative damping effect being so nearly equal to the total of the positive damping from all causes that the generation of oscillations may be stopped and started by said variation.

2. In combination, a regenerative tube system having inputand output circuits, a second tube having an input circuit and a transformer having a primary winding included in saidoutput circuit and a secondary winding included in said second-mentioned tube input circuit, said transformer having an adjustable air gap whereby the proportion of energy used for regeneration in said first mentioned tube can be varied, said transformer also having such 7 low permeability radio-frequency that the reactance of the primary winding thereof is substantially independent of variations in said air gap.

in testimony whereof, I have hereunto subscribed my name this 20th day of April, 1923.

MAX C. BATSEL. 

